Technical Field
This Patent Document relates generally to resonant sensing, and more particularly to testing resonant sensor circuits, such as resonant inductive sensor circuits.
Related Art
Resonant sensing systems include a sensor resonator and sensor electronics (resonant sensor circuit).
A sensor resonator includes a resonator configured for operation in a resonance state (resonant frequency and amplitude). The sensor electronics drives the resonator with an AC excitation current synchronized with resonator oscillation voltage to maintain resonance (sustained, steady-state oscillation), balancing a resonator loss factor represented by a resonator impedance.
Resonant sensing is based on changes in resonance state manifested by changes in resonator oscillation amplitude and frequency resulting from changes in resonator impedance, for example in response to a conductive target. That is, sensor response to a conductive target is manifested as a change in resonator impedance (loss factor); so that corresponding changes in resonator current drive to balance the change in resonator impedance, and sustain resonance oscillation, represent a sensed condition of the target (such as proximity, position or physical state).
An example of resonant sensing is resonant inductive sensing that uses a sensor resonator implemented as an LC tank circuit with a sensing coil inductor, and a resonator loss factor (which can be represented as a series resistance Rs). The sensor LC resonator, operated at resonance, projects a magnetic sensing field (magnetic flux energy). A conductive target interacts with the projected magnetic sensing field (and the coil inductor) based on the eddy current effect, so that sensor resonance is affected by a storage or loss in magnetic flux energy output from the sensing coil inductor, which corresponds to a change in resonator loss factor.